Prior oven designs use heaters which are either fastened to the walls or floor, or may even totally encompass the entire interior of the cabinet. All of these systems tend to create stagnant heat near the top of the cooking or heating chamber which just continues to get hotter, resulting in a large thermal gradient within the cabinet.
Positioning of heater elements and controls is generally dictated by whether the cabinet includes single or dual access doors as well as the fact that the heated air within the cabinet rises to the top. It has been found that convection heat flow is preferred for cooking purposes, since convection heat cooks the food more thoroughly and quickly, while radiant heat is used to store and tenderize food. Proofing is the process for adding dough and water during the cooking process to keep the dough from cracking when rising, and requires maintenance of a target temperature and humidity within the cabinet.
These design considerations are complicated by frequent opening and closing of the doors during use. Thus an ideal design would enable natural heat circulation; would reduce temperature variation within the cabinet; would allow ready access to the heaters for enhanced serviceability with reduced maintenance costs; and, would achieve the foregoing at greater efficiency by reduction in wattage used.
Prior art devices are not calculated to attain these goals or, if so designed, have not attained them.
U.S. Pat. No. 2,718,854, to Michaelis, 1951, discloses a bake pan or oven deck to provide a diffuse heat to eliminate burned spots with decreased heat by conduction and increased heat by radiation.
U.S. Pat. No. 3,197,185, to Beattie, 1963, is a heat furnace directed to heat treatment of glass.
U.S. Pat. No. 3,282,578, to Ulbrich, 1966, represents a liner for a furnace or kiln to absorb thermal shock.
U.S. Pat. No. 3,327,041, to Clune, 1964, is a heat shield pack with cylindrical heat shields of spaced-apart heat shield leaves of refractory material.
U.S. Pat. No. 4,209,569, to Brugger, 1980, is an aluminum baking form coated with aluminum oxide and the method of making same.
U.S. Pat. No. 4,648,377, to Van Camp, includes a gas fired blower and an improved, bifurcated heat exchanger.
The firing chamber of U.S. Pat. No. 4,978,295, to Vukovich, Jr., 1990, includes an upper ventilation aperture and an exhaust fan.
Accordingly, there is a need for commercial baking ovens and holding ovens with a chamber which can rapidly achieve a predetermined temperature with improved temperature maintenance capacity through repeated opening and closing of the cabinet in ordinary use and when the oven is in a thermostatically controlled power off mode.
It is therefore a principal object of the invention to provide a holding oven incorporating a heat sink formed of a first material with high thermal capacitance for rapid build-up and slow discharge of heat into an insulated space and, further incorporating a heat sink formed of a material with lower thermal capacity but having a thermal conductivity a multiple of four or greater times that of the first material.
Another object of the invention is to provide for natural heat circulation to diminish temperature variation and provide a radiant heat with convection heat flow within the cabinet.
Yet another objective is construction of an oven having better efficiency with reduced wattage per hour of use.
Still another objective of this invention is construction of a holding cabinet with heater elements positioned with consideration for either single or dual access doors, facilitating tear-down and serviceability of heaters, and resultant reduction in maintenance costs.
Further objects and advantages of the invention will become apparent from the following detailed description of the preferred embodiments and from the accompanying drawings.